1. Technical Field
The invention relates to a mixed light apparatuse and, particularly, to a mixed light apparatus for LED-based light sources.
2. Description of Related Art
Currently, because liquid crystal displays (LCDs) are thin, lightweight, long lasting, and consume little power, they are extensively used in a variety of electronic devices. However, because LCDs are not self-luminescent, backlight modules are typically required. Generally, backlight modules can be categorized as either direct-type backlight modules or edge-type backlight modules. Because direct-type backlight modules can provide high illumination in comparison with edge-type backlight modules, direct-type backlight modules are more widely employed in numerous applications.
Referring to FIG. 1, a conventional direct-type backlight module 10 includes a substrate 11, a light source 12 and a diffusion plate 14. The light source 12 is disposed on the substrate 11. The light source 12 can employ a plurality of point light sources (e.g. light emitting diode, LED) or a linear light source (e.g. cold cathode fluorescent lamp, CCFL). An LED array is extensively employed as the light source 12 for LCDs because the LED is resistant from mercury pollution, while exhibiting qualities of high color saturation and longevity. The diffusion plate 14 is disposed above the substrate 11 for allowing light emitted from the light source 12 to be uniform and providing light for an associated display panel.
The LED array consists of a plurality of red LEDs 12a, green LEDs 12b and blue LEDs 12c. The LEDs 12a, 12b, 12c are uniformly distributed on the substrate 11 according to the color of emitted light. Particularly, rows of red LEDs 12a, green LEDs 12b, and blue LEDs 12c are arranged in alternating fashion. Red, green, and blue light, is emitted from the light source 12 and mixed continuously until reaching the diffusion plate 14 to produce white light. A predetermined distance between the light source 12 and the diffusion plate 14 is required for mixing the emitted light and providing uniform illumination.
Because of a recent increase in demand for thin and lightweight LCDs, the distance provided for mixing emitted light has shortened, resulting in poor mixing, thereby producing a yellowish-blue light rather than the intended white light.
In addition, when a large number of red, green and blue LEDs are utilized for a large-scale LCD production, the white light emitted from such an LCD has low energy and color saturation. Moreover, the color of the mixed light in such manner cannot be adjusted as desired.
Furthermore, the LED acts as a Lambertian source and emits light over high radiation angles, i.e. ±90 degrees. Thus, it is common to use a lens over the point light sources to narrow the light beam. However, as of now, there is no suitable lens for completely converging light with divergent radiation angles. Therefore, if the light beam emitted from each low-power LED cannot be totally converged to the associated display panel, the illumination efficiency is consequentially lowered.
What is needed, therefore, is a mixed light apparatus for providing adjustable color light having improved color saturation, improved uniformity, high energy, and the ability to efficiently converge light with divergent radiation angles.
Corresponding reference characters indicate corresponding parts. The exemplifications set out herein illustrate at least one exemplary or exemplary embodiment of the present mixed light apparatus, in various forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.